Mobile phones, personal digital assistants (PDAs), digital cameras, MP3 players, and other portable electronic devices utilize SSL devices (e.g., white light LEDs) for background illumination. However, true white light LEDs are not available because LEDs typically only emit light at one particular wavelength. For human eyes to perceive the color white, a mixture of wavelengths is needed.
One conventional technique for emulating white light with LEDs includes depositing a converter material (e.g., a phosphor) on a light emitting material. For example, as shown in FIG. 1A, a conventional LED device 10 includes a support 2 carrying an LED die 4 and a converter material 6 deposited on the LED die 4. The LED die 4 can include one or more light emitting components. For example, as shown in FIG. 1B, the LED die 4 can include a silicon substrate 12, an N-type gallium nitride (GaN) material 14, an indium gallium nitride (InGaN) material 16 (and/or GaN multiple quantum wells), and a P-type GaN material 18 on one another in series. The LED die 4 can also include a first contact 20 on the P-type GaN material 18 and a second contact 22 on the N-type GaN material 14. Referring to both FIGS. 1A and 1B, in operation, the InGaN material 16 of the LED die 4 emits a blue light that stimulates the converter material 6 to emit a light (e.g., a yellow light) at a desired frequency. The combination of the blue and yellow emissions appears white to human eyes if matched appropriately.
Many processes manufacture LED devices from a semiconductor wafer, which includes many individual LED dies. The wafers are later cut to separate the LED dies, and then the individual LED dies are packaged. For example, the LED die 4 shown in FIG. 1B can be packaged by attaching the LED die 4 to the substrate 2 and wire bonding the first and second contacts 20 and 22 of the LED die 4 to contacts of the support 2. The converter material 6 is then deposited and a lens (not shown) can be formed on or attached to the converter material 6.
One drawback of such LED packages is that a separate dam or other structure is generally needed to contain the converter material 6. Another concern is that each LED die 4 is often mounted to a separate substrate 2, which is time consuming and requires more precise handling. Additionally, LEDs generally produce a significant amount of heat, and the different coefficients of thermal expansion between the LED die 4 and the substrate 2 can cause delamination or other damage to the packaged device.